GENERAL PLAN OF THE SERIES. 



This Series is pfimarily designed to aid the University Extension 

 Movement throughout Great Britain and America^ and to supply 

 the need so widely felt by students, of Text-books for study and 

 reference, in connection with the authorised Courses of Lectures. 

 Volwnes dealijig with separate sections of Literature, Science, 

 Philosophy , History, and Art have been assigned to representative 

 literary men, to University Professors, or to extension Lecturers 

 connected with Oxford, Cambridge, Lojidon, and the Universities of 

 Scotland and Ireland. 



The Mamials differ from those already in existence in that they 

 are not intended for Elementary use, but for students who have made 

 some advance in the subjects dealt with. The statement of details is 

 vieant to illustrate the working of general laws, and the developjuent 

 of principles ; while the historical evolution of the subject dealt with 

 is kept i7i viexv, along with its philosophical signifcance. 



The ref?iarkable success which has attended University Extetision 

 in Britain has been partly due to the combination of scieJitific treat- 

 ment with popularity, and to the union of simplicity luith thorough- 

 ness. This movement, however, can only reach those reside?it in the 

 larger centres of population, while all over the country there are 

 thoughtful persons who desire the sajne kind of teaching. It is for 

 them also that this Series is designed. Its aim is to stipply the 

 general reader with the same kind of teaching as is given in the 

 Lectures, and to reflect the spirit which has characterised the move- 

 ment, viz. the combination of principles with facts, and of methods 

 with results. 



The Manuals are also intended to be contributions to the Literature 

 of the Subjects with which they respectively deal, quite apart from 

 University Extension ; and some of them will be found to meet a 

 general rather than a special want. 



